So what exactly is the file format of your flat file DB?  As in, is "everything on one line", or "everything in a set number of lines", or "variable records"?

In regards to reading in a file:

open(FILE_HANDLE, ">>", "$filename") || die "ACK, GASP: $error_message
+\n";
my @data = <FILE_HANDLE>;
chomp(@data);
close FILE_HANDLE;
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will slurp the entire flat file DB in and remove the newline character(s) from each line (depending on the size of the file, slurping entire files may not be a Good Idea^TM).